Molding sand and process of using



45 viscosity of the Patented 35 1931 a 7 UNIT D.-mus- ROY cnoss, orKANSAS c'rrY, .mssoum, Assranoa r srLroA rnonuo'rs companion xnnsascrrY, mssoun'r, A o

onronanon or DELAWARE,

norm-no snunann rnocnss or usmo No Drawing.

This invention relates'to the production of a material for use asmoldingsand in steel,

iron, brass and other foundries. It ossesses the desirable properties toa'much higher degree than usual in molding sand, such as bonding value,permeability, freedom of gas pas sage, refractoriness, strength,cohesiveness and the like.

In molding sand, thequality and quantity of binding agent present are ofgreat imortance. With an Ideal agentacore is readi y molded wet, standsup well dry, is readily disintegrated after use and the voids betweengrains are sufficiently open to permit free passage of steam and-gases.Clay is the usual bonding agent butfit has. been found that bentonite inthe sand-has some advantages.

The present invention relates to molding sand containing bentonite,plastic clayjor a 120 mixture of clay and, bentomte, a's'a binder;

and it rests on the observationuthat certain additions greatlyimprovethe quality and Good rmolding utility of these binders. sands maybe made by ,mixing ordinary sharp sand with a little ordinary clay andadding small proportions of bentonite ale ter'ed as to its properties bythe presence'of certainaddition agents. Among the most useful of theseaddit ons are ma gnesmmnxide. a0 (magnesia) and Pomnt. Portland cementcan be regarded asco sisting of calcium silicate and calcium aluminatein rea'c tive form. Either is useful for. the present purposes. In usingPortland cementas an addltion agent, as a eneral thing, suflicientcement is added to't e bentonite to greatly increase the gelling valuein the "presence of; ical amountto be added." is 5 water. A

per cent of t e bentonite. Ma esium oxide 40 acts in the same way, butordinarily not so great an amount is required. A. ty ical amount is 1lpier cent. Both of these addition agents shou of course be finely und.'These addition a gm nts greatly increase the given by bentonite withwater. In the 0 owing table are shown the proportions of bentonite, withand without addition agent, necessary to obtain a given viscos1 with agiven amount of water. The

- materia used in obtaining the figures in the Application filed July22, 1929. Serial 1T0. 880,264.

first column is a commercial preparation of bentonite containing 2 percent of ordinary fine Portland c'eme'nt" in; admixture. The sec ondcolumn represents the bentonite without the admixture. The viscositiesexpressed'in .5) .thelthird column are thosegiven by th i Michaelviscosiineter with No. 30-wire and 3 disc; the viscosity being expressedin angular degrees.

3 proportion tomte insand used for oundry'pu'rpos'esi f 'Fromthe table,it will be seen that the ad-, dition of Portland cement great? increasesthejgellingpropert and this is, oundtobe a to the ondin property ofbenif.

Ina general we it will be noted thatthe'j a gelling value an hence thebonding value of. I

the treated bentonite is several times that of the untreated; 1 percent'of treated bentonite giving twice the'viscosity'of a 2 per centmix; t'u're-of ulitreatedbentonite, for'example. By I a treatment withcalcium silicate, with ma l -nesium oxide or with other improver of thissort, the bonding value of bentonite infoundry sand is greatly enhanced.

- v In a typica embodimentjof the present invention making an excellentmolding sand,

90 percent of good unbonded sandris mixed with 7.5 per cent of fire clayand 2.5 percent,

of the treated bentonite referred to. How-,

ever the ,proportionsused vary with the particular work to'be done bythe molding sand and the exact use to which the sand is to be put. Inthe case of heavy castings, it is ordinarily desirable to use a eateramount of the [treated 'bentonite. In t 0 case of H ht cast- ,ins, theamount can be decreased.

ikewise, v 1 where increased porosity is desired, a larger as amount ofthe bentonite pre aration is used.

In many cases, it is also esir'able to add a small amount of organicmatter to the mix. i

Often this is already contained in the clay used-. If organic-matter isadded it may be m l CROSS'REFERENCEs'i- A A PAT ENT 1 in the nature ofordlnaryhuxr us,'or in the nature of finely ulverized bituminous coal,preferably smlt ing coal, grahamite, gilsonrte, drying oils, resinsoreven rubber latex.

g Latex is particularly valuable in increasing the strength of the bondwithout decreasit cement on the bentonite which gives the im-"rovedproperties noted, is not known; nor

is it known whether chemical action occurs;

A com lete analysis of the mixture above reierre' to, conslstingofcommercial bentolfite with ,2. per cent of addedPortland ceasfollows:

Slag, cement, calciumpsilicate, etc. may be in improving low gradebentonites; or

erties.

What'I claim is:-

1.. A molding compound comprising finely divided inert material andbentonite treated to heighten its gelling power with an alkain givingplastic clays the bentonite propn e 2. A dry molding compound includingunbonded sand, and bentonite containing an inorganic modifyindg agent ofalkaline properties, the said mo fying agent producing an increase inthe gelling powerof the said *3. A moldin co'm ound including unbondedsand, c ayian bentonite containing a small pro ortion of added Portlandcement.

4. A mo ding compound comprising the following substances inapproximately the stance of thenature of magnesium was: followingproportions: 90 per cent sand, 7.5 Ines-0n i 'tion. 6.0 per centclay-and 2.5-percent bentomte con- Silica 10,), 58.2 taining an additionagent enhancing its gelas Alumina (Al,0,)' 21.9 io m sp p es. 1 a Ironoxide Fe,0,)- 3.8 ,5. In the manufacture of molds for Lime (CaO 5.9foundry purposes, the process which corn- Magnesia M 2.4 prises treatingbentonite with an 1 norgamc Sulphur 0.9 modifying afizlantto enhance itspowchlorides Cl 0.2 (are, mixing e treated bentonite wit sand,Alkalie's'( a, (K,O) 0.7 claey and water, shaping drying and baking. Thecomposition of claim 1 w1th.an a

A.- preparation of difierent analysis but I havin even more active prortie's is obtaine by mixing bentonite'wit 1 rcent orso ofcommercialmagnesia. Various active forms of calcium aluminate and of calcium osilicate may be used in lieu of either Portland cement or magnesia.These materials may be obta ned zeolites n11t fz: we see an er urposes.is r be noted that iie'ceme'nt, e magnesium oxids, the calcium aluminateand the calcium silicate are all bodies of alkaline reaction andcontaining an alkaline earth. V Moldinglsands made acco. to thisinvjention t at-is'by mixing sau cla and m treated bentonite, uponbaking and mo ding,

iurmshcore's of unusually desirable propermodified to its dition of or cmatter.

. 7. A moldii ig compound comprising unbonded sand, clay, bentonite andorgamc'mat ter, the said bentonite being treated with .an alkalineneiu2oxide.b (l be to core in er com rising n m gellm' g llfifwer by theaddition of a small amount of aline reacting material selected fromagroup comprising magnesium onde, calcium v ca cium silicate, Portlandcement and blast furnace slag.

In testimony whereof, I have hereunto at fixed signs 'ture.

a nor caoss.

i o'rthepurpose oithisspeciflcationbentonite ma'y b'edefined asahydrated silicate o1 as alumina whicmiwhen' mixed with 200 per.ifmixture, or a having a viscofity on iMacMichael (usin'gN'o. 30 ijeans disc) of25 e :Eul as additions to bentonite and to plastic clay.Galciumsilicate made from a'water.

.cent orniore'ot water, will form a gelatinous 1 soluble calcium'salt,such as calcium chlorid and sodium silicate (waterglass) is a par-g ltieularly good addition agent for bentonite. a

substance of the nature of mag-.

alummate,

7 use

